Atrioventricular Junctional Premature and Escape Beats with Altered QRS and Fusion

Abstract

The interval between an ectopic QRS and a retrograde P wave measured in simultaneous esophageal and other leads may help to identify beats which originate in the atrio-ventricular (A-V) junction. In six cases beats which seem to originate in the A-V junction are associated with a QRS which differs in configuration from the QRS of sinus origin, and in each case atrial premature systoles which give rise to normal QRS complexes occur in tracings which contain the A-V junctional beats also. Comparison of the QRS of the atrial premature systoles with the QRS of the A-V junctional beats with respect to the time of occurrence in the cardiac cycle and the duration of the preceding cycle makes it seem unlikely that the altered QRS of the A-V junctional beats can be explained by aberrant conduction during incomplete recovery. In five of the cases, fusion QRS complexes occur, suggesting activation of the ventricles partly by an impulse of sinus origin and partly by the impulse of A-V junctional origin. These observations support the interpretation previously made by others that impulses of A-V junctional origin may reach the ventricles by pathways other than the usual A-V pathway. If such beats as are described here occur at all frequently, then the diagnostic value of fusion, heretofore considered an almost conclusive criterion of a ventricular focus, may be impaired.